Matthew Aidekman

This seems like an extremely simple idea to me but I cant figure it out at all

if I have a desired left, top, right, bottom in pixes. how do I get the GL space position/scale for it?

I can be in ortho 2 if you need me to be... (the hook to my next pop tune)

sorry in advance for asking for something stupid

if I have a desired left, top, right, bottom in pixes.  how do I get the GL space position/scale for it?

I can be in ortho 2 if you need me to be...  (the hook to my next pop tune)

ltrb-in-pixels

> if I have a desired left, top, right, bottom in pixes. how do I get the

You can set up the opengl projection so that you can draw things using

integer pixel coordinates, and omitting whatever rotation or scaling is

going on in the rest of you scene. This is my code using Lua, but its

straightforward to convert it to JS or jit.gl.sketch commands:

    gl.Ortho(0, 640, 480, 0, 0, 1) -- window dimensions in pixels

    gl.MatrixMode("MODELVIEW")    

Whatever you draw in between those function calls will appear in 2D. (0,0)

is the top left corner in this example, but you can choose whatever corner

you prefer to be your origin by changing the arguments to glOrtho(). Note

that this example uses a fixed 640x480 context.

On 8/18/07, Matthew Aidekman  wrote:
>
>
>
> if I have a desired left, top, right, bottom in pixes.  how do I get the
> GL space position/scale for it?
>
>
>
Hi Matt,

You can set up the opengl projection so that you can draw things using
integer pixel coordinates, and omitting whatever rotation or scaling is
going on in the rest of you scene. This is my code using Lua, but its
straightforward to convert it to JS or jit.gl.sketch commands:

function uSetOrtho2D()
	gl.MatrixMode("PROJECTION")
	gl.PushMatrix()
	gl.LoadIdentity()
	gl.Ortho(0, 640, 480, 0, 0, 1) -- window dimensions in pixels
	gl.MatrixMode("MODELVIEW")
	gl.PushMatrix()
	gl.LoadIdentity()
end

function uResetOrtho2D()
	gl.PopMatrix()
	-- restore previous projection
	gl.MatrixMode("PROJECTION")
	gl.PopMatrix()
	gl.MatrixMode("MODELVIEW")	
end

Whatever you draw in between those function calls will appear in 2D. (0,0)
is the top left corner in this example, but you can choose whatever corner
you prefer to be your origin by changing the arguments to glOrtho(). Note
that this example uses a fixed 640x480 context.

sorru I havent been on the board more. hofstadter's rule applies

>From a Jitter object, you can use @transform_reset 2 to get

coordinates from [-1, 1] across both dimensions and then scale/bias

approproately to get pixels. I belielve all jit.gl objects have a

dest_dim attribute (or something similarly named). You can use this

> sorru I havent been on the board more. hofstadter's rule applies

>From a Jitter object, you can use @transform_reset 2 to get
coordinates from [-1, 1] across both dimensions and then scale/bias
approproately to get pixels.  I belielve all jit.gl objects have a
dest_dim attribute (or something similarly named).  You can use this
to figure out the window size.

On 8/18/07, Matthew Aidekman  wrote:
>
> very sneaky...  me liky!
>
> sorru I havent been on the board more. hofstadter's rule applies
>


LTRB in pixels